JPS61169128A - Phenolic resin binder for shell mold and resin coated sand for shell mold - Google Patents

Abstract

PURPOSE:To obtain a casting having a good casting surface without using a mold coating material by compounding carbon powder with a phenolic resin to form a phenolic resin binder for a shell mold. CONSTITUTION:The phenolic resin binder for the shell mold is formed by compounding the carbon powder with the phenolic resin. A novolak type phenolic resin, resol type phenolic resin, etc. are used for the phenolic resin. The carbon powder to be compounded with the phenolic resin is >=1 kinds among petroleum coke, petroleum pitch coke, natural graphite, anthracite, artificial graphite, carbon black, resinous coal, precursor and silicon carbide.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to a phenolic TJF fat binder for shell molds and a resin coated sand for shell molds.

[Background technology] Shell molds are produced by bonding molding sand such as silica sand with a fat binder.This shell mold has excellent properties such as a smooth casting surface and good dimensional accuracy. The binder for this shell mold is generally a mixture of phenols and aldehydes in a molar ratio of 1: (1.6 to 0.0).
7 Borac-type phenol fj (fat, or solid obtained by adjusting the molar ratio of phenols and aldehydes to 1:1 to 3 and reacting under an alkali catalyst) The resol type 717-R01 resin is used, and the 7volac type phenolic resin is blended with hexamethylenetetramine as a hardening agent, and the resol type phenol resin is mixed with heated molding sand by CH1 and caking. The resin-coated sand coated with a coating layer of the agent is poured into a shell mold by sprinkling or filling the resin-coated sand into a heated mold to melt and harden the binder. It is molded as follows.

However, when casting products using such a shell mold, if the high-temperature molten metal comes into direct contact with the surface of the shell mold, the molten metal may be inserted or baked at the interface between the molten metal and the shell mold, and the casting surface of the fIIj product may be damaged. In addition, there is a risk that the shell mold will undergo rapid thermal expansion at the interface with the molten metal, causing cracks, and that the molten metal will be inserted into the cracks.

Therefore, in order to deal with these problems, protect the shell mold from the high temperature of the molten metal, and at the same time smooth the surface of the shell mold to improve the casting surface, for example, Japanese Patent Publication No. 58-28
015, Japanese Patent Publication No. 58-19376, Japanese Patent Publication No. 58-47251, Japanese Patent Publication No. 58-4.7252, etc., graphite, Norcon, and aluminum oxide have been conventionally used on the surface of shell molds. It is done by applying a molding agent containing powder or the like.

However, since coating agents are used by dispersing them in a solvent such as real alcohol that has been dispersed in water, the process of dispersing, applying and drying the coating agent is complicated. This poses a problem, especially during dispersion work, where dust is created and degrades the work environment. In addition, when a mold coating agent is used dispersed in a solvent such as alcohol, there is a problem that the danger of fire etc. increases, and conversely, when a mold coating agent is used dispersed in water, the application is poor and It takes a long time to dry, and moisture tends to remain, causing problems such as cracks, poor casting surface, and reduced strength. Furthermore, since the mold coating agent is used by applying it, if the mold surface of the shell mold has a complex uneven shape, it is not possible to apply the mold coating agent with a uniform thickness, resulting in uneven coating. There is also the problem that the effect of the coating agent may be halved or the layer of the coating agent may separate from the surface of the shell mold.

[Objective of the Invention 1] The present invention has been made in view of the points mentioned above, and provides 7. The purpose of the present invention is to provide resin binders and resin coated sand.

[Disclosure of the Invention] Phenol O (
The fat binder is characterized in that it is composed of a 7-el resin mixed with carbon powder, and the resin-coated sand for shell molds according to the present invention is characterized in that the surface of the molding sand contains carbon powder. The present invention is characterized in that it is coated with a coating layer made of a phenolic resin binder.The present invention will be described in detail below.

As phenolic resin, novolac type phenolic resin,
It is possible to use either a resol type 7 ether resin or a mixture of a novolac type phenol resin and a resol type phenol resin. Examples of the carbon powder to be blended with this phenol resin include petroleum copolymer resin. Kusu,
Examples include petroleum pitch coke, natural graphite, anthracite, artificial graphite, carbon black, resin charcoal, precursor, etc., and one or more of these may be used in combination. Furthermore, silicon carbide, which is a carbon compound, can also be used as the carbon powder. The particle size of carbon powder is 200 from the viewpoint of uniform mixability.
It is preferably less than μ.

This carbon powder is mixed and dispersed with a 7-enol resin to prepare a 7-enol resin binder for shell molding, and the carbon powder is blended with the liquid 7-enol resin.

Specifically, carbon powder is blended and mixed during the process of condensing phenols and aldehydes to prepare a 7-el resin, or carbon powder is mixed before taking out the condensation reaction product from the reaction vessel. The phenol resin can be blended and mixed, or the phenol resin can be granulated and cooled, then heated and melted, and carbon powder is added and mixed there. Furthermore, the phenol resin can be dissolved in a solvent and carbon powder can be produced in this state. can be blended and mixed. The mixing ratio of phenol resin and carbon powder varies depending on the required performance of the shell mold, but generally speaking, the mixing ratio of carbon powder to 100 parts by weight of 1 part of phenol resin (1 part by weight of fat) is Parts by weight are preferred.

``Phenol 0 (fatty binder) for shell molding is prepared as described in ``1. Obtain coated sand for molding.To coat the sand with phenolic resin binder,
This can be done by dry hot foot method, cold coat method, semi-hot coat method, powder solvent method, etc. In the dry hot coating method, the solid phenol resin containing carbon powder is added to sand heated to 130 to 180°C and mixed, and the solid phenol resin is melted by heating with the sand. The surface is wetted and coated as a coating layer, and then cooled while retaining this coating layer to obtain a granular and free-flowing resin coated sand.

In the cold coating method, the carbon powder-containing phenolic resin is dissolved in a solvent such as methanol to form a liquid, which is added to sand and mixed, and the solvent is evaporated to obtain resin-coated sand. In the semi-hot coating method, a liquid phenol resin containing carbon powder dissolved in the above solvent is added to and mixed with sand heated to 50 to 90°C to obtain resin coated sand. The powder solvent method involves pulverizing a solid carbon powder-containing phenolic resin.
This pulverized resin is added to sand, a solvent such as methanol is further added, and the mixture is mixed to obtain resin coated sand. Although granular and smooth Rennon coated sand can be obtained using any of the above methods, the dry hot coating method is preferred from the viewpoint of workability. The mixing ratio of sand and phenolic resin varies depending on the required performance of the shell mold, but it is generally preferable to mix the phenol resin to 1 to 7 parts by weight in terms of resin solid content per 100 parts by weight of sand. Here, since the carbon powder is pre-blended and mixed with the phenolic resin binder, it is possible to mix a large amount of carbon powder with the sand while blending it with the phenolic resin binder. This makes it possible to obtain Lennon coated sand containing carbon powder. In addition, during this mixing, a curing agent, various coupling agents such as a silane coupling agent to make sand or carbon powder compatible with the phenolic resin binder, wax, etc. may be added as necessary. It ends with.

By sprinkling or filling the thus obtained Lennon coated sand into a heated mold according to a conventional method and melting and hardening the phenolic resin binder,
A shell mold is formed by the binding action of sand by this binder. The shell mold thus obtained can be cast without the need to apply a mold coating. In other words, the carbon powder contained in the 7-el resin binder has high thermal conductivity, and even if the surface of the shell mold is rapidly heated by the action of the molten metal, this heat will not be absorbed. Heat is transferred to the back side of the shell mold by the carbon powder, preventing the shell mold from rapidly heating up at the part that comes in contact with the molten metal and causing rapid thermal expansion, and preventing the shell mold from cranking due to rapid thermal expansion. Furthermore, due to the excellent thermal shock resistance of carbon powder and the poor wettability of carbon powder to molten metal, the molten metal is prevented from being inserted into the shell mold, and the casting surface of the casting can be improved. It is something that becomes.

In this way, carbon powder has poor wettability with molten metal, so it has good mold releasability from castings after casting, making it possible to improve the release of sand from castings, and also to remove the shell mold from the mold. This means that the mold releasability during molding can also be improved.

Therefore, it is possible to obtain a casting with an excellent casting surface without the need to apply a coating agent to the shell mold during casting.

Next, the present invention will be specifically explained using examples.

and 1 juice 1 940 g of phenol in a 2 liter four-ton flask, 3
7% formalin 6488 and 5.6 g of sulfuric acid were added and refluxed for about 90 minutes. After the reaction solution was emulsified,
After continuing the reaction for 0 minutes, atmospheric dehydration was started and the temperature was increased to 150°C.
dehydrated to. Next, dehydration was further performed at a reduced pressure of 100 Torr until the internal temperature reached 150°C.

Next, 100g of natural graphite powder with a particle size of about 50μ was carefully added, mixed well for 30 minutes, then poured into a vat, cooled, and then mixed with a particle size of 0.5~3. , the first particle size of Il
I crushed it.

The softening point of the obtained natural graphite-containing novolac type phenol fat binder was 88°C, and the content of natural graphite powder was 10
%Met.

Dog 11” - Example 1 except that the amount of natural graphite powder added was 425 g
I did the same thing.

The softening point of the obtained natural graphite-containing novolac type phenolic resin binder was 93°C, and the content of natural graphite powder was 30%.
Met.

X operation 1 Take 1.5 kg of the 7-borac type phenolic resin with a softening point of 85°C and mix carbon powder obtained in Example 1 into a 2 liter flask, heat and melt it until the internal temperature reaches 140°C. When the temperature reached 1,000 g of the same natural graphite powder as in Example 1 was carefully added, and the mixture was thoroughly stirred and mixed for about 30 minutes.

The softening point of the obtained natural graphite-containing 7-borac type phenolic resin binder was 96°C, and the content of natural graphite powder was 60%.
Met.

Line engraving ↓ 470g of phenol in a 2 liter four-eye flask, 3
7% formalin 827g, 28% ammonia water 110g
was added, the internal temperature was raised to 80°C over about 60 minutes, and the reaction was continued for 4 hours.

Next, dehydration was performed under reduced pressure at 70 Torr, and the internal temperature was 65°.
When the temperature reached C, artificial graphite powder with a particle size of 10μ was added to the
5 g was added, and further vacuum concentration was performed up to 90°C. Immediately pour it out into a vat and cool it, then add 0.5 to 3
It was coarsely crushed to a diameter of +11111.

The softening point of the obtained resol type phenol 431 fat binder containing artificial graphite was 83°C, and the content of artificial graphite powder was 3.
()%Met.

Jitsu-i Masu-1 Novolac type phenolic resin 1300 with a softening point of 90°C
Take 4 g [1 flask] and add 700 g of methanol to it.
g was added and dissolved well.

Next, 560 g of the same artificial graphite powder as in Example 4 was added to this and thoroughly mixed and dispersed.

The viscosity of the obtained artificial graphite-containing novolac type phenolic resin binder face at 25° C. was 30 poise, and the content of artificial graphite powder was 30% in terms of solid content.

A solid resol type phenolic resin 1300Fi with a softening point of 78°C, which was prepared by reacting in the same manner as in Example 4 except that no artificial graphite powder was blended, was placed in a four-eye flask, and 700 g of methanol was added thereto. Dissolved well.

Next, 560 g of coal pinch coke powder was added to this and well dispersed.

The viscosity of the obtained resol type phenolic resin binder varnish containing coal pitch coke at 25°C was 40 poise, and the coal pitch coke content was 30 poise in terms of solid content.
%Met.

A coal pitch coke-containing novolac type phenolic resin binder varnish was obtained in the same manner as in Example 5, except that coal pitch coke powder was used instead of the artificial graphite powder. The viscosity of this material at 25°C is 50 poise,
The content of coal pitch coke powder is 30% in terms of solid content.
Met.

11 Suzu Y2 L 30 kg of 7 ratari monosilica sand heated to 140°C was charged into a Whirl mixer, 900 g of the novolak type phenolic resin binder obtained in Example 1 was added thereto, and after kneading for 30 seconds, hexamethylenetetramine was added. 145g for 30
It was dissolved in 0 g of water and added, and kneaded until the clumps of sand grains collapsed. Next, 15 g of calcium stearate was further added to this, and after kneading for 30 seconds, the mixture was discharged for aeration to obtain a Lennon-coach sand.

Tue-Example-Turney L-/Bora-nk type 7r obtained in Example 2, /-/Lenone coated in the same manner as in Example 1-1 except that the resin caking cutting was used. Got a sandwich.

EXPERT - LEGEND - VOICE A Lennon coated sand was obtained in the same manner as in Example 1-1, except that the 7-borac type phenolic resin binder obtained in Example 3 was used.

Practical Example/I-1 Renone coated sand was prepared in the same manner as in Example 1-1 except that the vIJ-resol type phenol 4j1 fat binder was used in Example 4 and hexamethylenetetramine was not used. IJtko.

Actual Example 11-5-=1 7 lattice silica sand heated to 80°C 3 (IKg was charged into a whirl mixer, 7 Borac type 7 Emer fat-disintegrating binder varnish obtained in Example 5) Hexamethylene 1 lamin in 150H 110g of calcium stearate was added and kneaded until the sand grains disintegrated.
After adding and kneading for 30 seconds, the mixture was discharged and aerated to obtain Lennon-coach sand.

Resin coated sand was obtained in the same manner as in Example 5-1 except that the resol type phenolic resin binder varnish obtained in Example 6 was used and hexamethylenetetramine was not used. Ta.

Tue-I) This-1 - Resin-coated sand was obtained in the same manner as in Example 5-1 except that the 7-borane type phenolic resin binder varnish obtained in Example 7 was used.

Example 1 - Resin coated sand was obtained in the same manner as in Example 1-1 except that natural graphite powder was not used.

1 phrase example -? - Resin coated sand was obtained in the same manner as in Example 4-1 except that no artificial graphite powder was used.

” - Examples 1-1 to 7-1 and Comparative Example 1.2
Various tests were carried out using the Lennon-coach nd sand obtained by the method.The results are shown in the following table.

In the following table, fusion, df, ('C) is I A C
T test method 5M-1, room temperature 1111 lf strength (Kg
/CII+2) is based on JACT test method C-1, and the rapid thermal expansion coefficient (%) is measured at 1000°C in N2 gas based on JACT test method SM-7. Each test was performed at different temperatures. The strength (K g/cm2) of hot bending is JACT test method S M
-4 The test piece prepared in step 4 was placed in an electric furnace set at 1000°C, treated for 1 minute, and then heated to 1000°C.
This was done by measuring the bending strength at C. Oxidation resistance was determined by placing test pieces (20φ x 50 + nm) prepared according to JACT test method 5M-7 in an electric furnace heated to 1000°C for 5 minutes, taking them out, cooling them, and placing them in a vibrating sieve. After shaking for 1 minute, the weight was measured, and the weight % of the residue was calculated using the following formula for evaluation.

Weight after treatment/Weight before treatment x 100 (%) Judgment of casting surface is made using Lennon coated sand with an inner diameter of 100φ,
Height 100 +11111. This was done by preparing a crucible with a wall thickness of 20 m+n, pouring hot water at 1000°C into the crucible, cooling it, and then observing the cast surface of the finished casting using a 14-degree lens.

As a result of the table, it was confirmed that the rapid thermal expansion coefficient of each example was smaller than that of the comparative example, and that it was effective in preventing cracks from forming in the shell mold. It is confirmed that castings with good skin can be cast.

[Effect of the invention 1 As described above, according to the present invention, the surface of the shell mold is rapidly heated by the action of the molten metal poured into the phenol fj (because the fat binder contains carbon powder). However, this heat is transferred to the back side of the shell mold by the highly thermally conductive carbon powder, preventing the shell mold from rapidly heating up and causing rapid thermal expansion at the part that comes into contact with the molten metal. This completely prevents the shell mold from cracking due to expansion, and the carbon powder's excellent thermal shock resistance and the poor wetting of the carbon powder to the molten metal prevent the molten metal from entering the shell mold. Therefore, it is possible to improve the casting surface of the casting.Therefore, when casting, there is no need to apply coating agents that have various problems to the shell mold, and the casting surface can be improved. This is something that can be obtained.

Claims (3)

[Claims] (1) A phenolic resin binder for shell molds, characterized by comprising a phenol resin mixed with carbon powder. (2) Carbon powder is petroleum coke, petroleum pitch coke,
The phenolic resin binder for shell molds according to claim 1, characterized in that it is one or more of natural graphite, anthracite, artificial graphite, carbon black, resin charcoal, precursor, and silicon carbide. (3) Resin-coated sand for shell molds, characterized in that the surface of molding sand is coated with a coating layer made of a phenolic resin binder containing carbon powder.